Hello all, new to this form. I am trying to get my GTA back on the road so I can complete the motor break in. The car has complete new wiring and motor swap done by others, I just purchased the vehicle. It was running decent until I cut the ing bypass wire to set timing because the set timing harness had been buried in conduit and I added a connected behind the ecm. Immediately after the motor will crank but not start. I have checked the following:
Fuel pressure is good
TPS voltage is good
VATS is disabled on the promSpark at cylinder 1 tested with a timing light and car will fire but not run on starting spray Fuses good and power on both injector banks tested at ECM
Replaced icm and then entire distributor
12V on both orange wires at ECM
Tried different ECM and proms
Continuity on B5 dist reference wire
The car has new injectorsHave good ground on all ECM grounds (except ground to burn off relay) I am at the end of my capabilities and any insight will be awesome. Thanks!

 

Any power at pin a6 with the key on ?

 

I have 12v at A6.

 

Is the prom on a piggyback adapter where it can be removed and the memcal still attached. This would put the ecm in limp home mode and the injectors should fire. Sounds like you covered it all.

 

Nevermind the last suggestion. Even though you have spark the icm could be faulty.

 

I have replaced the icm and then an entire new distributor. I never tried pull the prom out, just switched memcals. Could it be a VATS issue even though it was supposedly tuned out? Weird that it would suddenly show up. Another thing that happened at the same time it stopped starting was the TPS bound up on the throttle bracket and bent it up. I got a high TPS voltage code but since replaced the TPS and volts seems good.

 

Since it fired up with the vats disabled memcal I’m thinking that’s not the issue. I can’t imagine what it can be. You have tried all the necessary steps.

 

I wish there was a way I could test the reference pulse to the ecm. I might have two screwed icms I guess.

 

That sounds unlikely, I think the reference is a tach signal just a guess. Looks like it’s a zero to 1.5v signal so cranking you should see voltage.
http://chevythunder.com/fuel%20injec...ecm%20#1227165)

 

It’s a square wave signal so only a scope or maybe a fluke would be able to see the signal. You could see the cranking rpm with a scanner too. The injectors won’t pulse until 400 rpms are detected witch in sure it’s cranking faster than that.
http://home.earthlink.net/~cliff_har...eforms.html#B5

 

Good info on those two links. Thanks!
I am going to check all injectors yet. I am sure I am missing something. I will also try get my hands on a scanner; seems to be hard to find.

 

Unplug all the injectors to see if you have injector pulse. Shorted out injectors will cause the injector driver to shut down. Unplugging the injectors will save you from ohming them atleast for testing . If they are the original grey body injectors multecs they are known to short out. Hopefully that’s your gremlin.

 

They are new Acell Injectors but it will be worth a check. Thanks!

 

So I hooked up a scan tool, it connected to the computer correctly and was displaying in live time as the TPS voltage changed appropriately with throttle movement, When I cranked the motor there was no change in the RPM displayed. When I connected a multimeter to B5 distributor reference wire I got .1 volts when cranking not 1.5V running like GM thunder chart suggested.

Could it be a ground that is messed up serving the ICM? Im going to figure out how to test the ICM before I try replacement #3

 

I can’t think of anything else to try. The tps reading correctly is good. I think it takes 4v or higher to disable the injectors.

 

Quick update; found the issue. There was a slight short on the black/red ground from the ecm to the icm that was taking our the entire reference pulse. Reran the wires and it runs.